Study of composition and structure of cadmium sulfide films prepared by chemical precipitation from solution

The process of formation, the composition and structure of films and deposits of CdS precipitated on glass supports from reaction mixtures containing a cadmium salt, and alkali, ethylenediamine and thiourea was investigated. The composition of the films and deposits was studied by X-ray phase and chemical analyses, and infrared spectroscopy. It was established that 78-92% of the films consist of α-CdS and contain a CdCN2 impurity. In the deposit, which was obtained under conditions where the formation of cadmium hydroxide is possible thermodynamically, a basic salt, close in composition to CdClsub(0.5)OHsub(1.5) was found. Films nucleate both by the mechanism of heterogeneous nucleation with the participation of the basic salt and by a homogeneous mechanism. The nucleation mechanism affects the behaviour of films in solutions of NH4OH and HCl. The films grow by crystallization of CdS on a support, therefore they contain much less impurity than the deposits. The CdCN2 impurity forms an independent, finely dispersed phase, which is, in the course of the film growth displaced onto the surface and into the intercrystalline spaces. Textured films with the C-axis perpendicular to the support were obtained on a glass support in all the conditions studied